


Unhealthy

by Cerberusia



Series: Dark Voltron Week 2017 [3]
Category: Voltron: Legendary Defender
Genre: Dubious Consent, F/M, Incest, Sibling Incest, Unreliable Narrator
Language: English
Status: Completed
Published: 2017-01-15
Updated: 2017-01-15
Packaged: 2018-09-17 17:40:28
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 2,408
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9335483
Author URL: https://archiveofourown.org/users/Cerberusia/pseuds/Cerberusia
Summary: Matt and her, two halves of the same whole. Nothing could break them apart.





	

**Author's Note:**

> For Day 3, 'Unhealthy Relationships/Consent Issues'. This has both!

"I've just met your brother! Are you two _twins_?" Mariella the new girl slides into her seat just as the bell rings. She's acted like she wants to be friends with Katie ever since she started, which is nice, especially since she's proving pretty popular in their year. Katie can do without friends - and has done it before - but she'd rather have some than not.

"No," says Katie as Mrs. Calverly strides in wearing a very unflattering skirt and they all start to take out their pens, "he's three years older than me. But I'm sure he'll be pleased to hear that you think he's only fourteen."

Mariella giggles. She's a pretty girl with long black hair and very thick eyelashes. Katie's in her dorm, and she's seen that Mariella's pajamas have bunny rabbits on them. They suit her.

"You look so much alike!" Mrs. Calverly is handing out books, so she leans in to whisper: "Actually, he's kinda cute!"

" _Children_ ," Mrs. Calverly announces grandly, so there's no time for Katie to reply - but she's suddenly quite certain that she and Mariella can't be friends at all.

~*~*~

Contrary to the stereotype of cold showers and five-mile runs, boarding school is actually pretty fun. Matt and Katie both join the robotics club and try to avoid as much sport as they can. They like their subjects and they like their friends, though Katie is looking forward to having a single room next year. Exeat is every three weeks, and they get to go home and eat home-cooked food and sleep in their own beds.

Or, specifically, _not_ in their own beds. Matt has a double bed - for the growth spurt that never came - and around midnight, when their parents are already asleep, Katie crawls in and cuddles up with her brother. She misses this when they're at school: it's a lot more difficult to share a bed when that would require Katie to sneak out of her dorm and the girls' house and into the boys'.

Often, Matt pretends to be asleep. He sprawls over his mattress, making it difficult for Katie to get in beside him. She just shoves him over and makes room for herself, curled up against his back, feeling his body heat. His hair tickles her nose.

" _Katie,_ " he mumbles, but doesn't kick her out. Occasionally he threatens to tell Mom and Dad, but she knows he's only teasing.

At school, her friends always say how surprised they are that she spends so much time with Matt.

"Look at the brothers and sisters here with two or three year age gaps," says Anabelle, the aspiring statistician among them. "Most of them can't _stand_ each other. The only siblings I know who are as close as you and Matt are would be the twins."

Everybody nods. The twins are two boys in the year below who basically only talk to each other. And they talk _all the time_. Katie overheard the Languages department complaining about it over lunch. But they're also mathematical geniuses, apparently, and this is a school designed for exactly that. It's why Katie has been able to make real friends here: she can actually have a _conversation_.

"The first thing I said when I saw Matt was how they looked like twins!" Mariella is painting her nails shell pink with great concentration. After the comment she'd made about Matt, Katie had quickly set about finding her a more suitable object of affection. Henry and Mary are now the darlings of the school, and Katie and Mariella are still friends. Which is fortunate, because she's the only one among them who can reliably take apart a car engine.

Twins. She likes that: Matt and her, two halves of the same whole. Nothing could break them apart.

~*~*~

"Are you going out?" Mom asks.

"Nope! Just came to make Matt some coffee." Katie presses the relevant buttons on the coffee maker and leans back against the counter. She pretends she can't see Mom eyeing up her outfit. "Man, it's hot."

"We've got the AC going full blast, but I guess there's only so much it can do in the middle of the desert." Mom sips her iced water. Katie can see that she's relieved she won't have to talk to her daughter about wearing short-shorts out of the house. When Mom met Dad, she had dyed red hair and ripped tights: she once told Katie she was glad she didn't go for wearing revealing clothes, because she'd feel a hypocrite if she declared them inappropriate.

"How's he doing? Still on stoichometry? Tell him to draw diagrams: it aids memorisation."

"Mm, I think he's taking a break to make notes on thermodynamics." The coffee machine ceases its whirring. "OK, I'm going to take this up to him. At the rate he's going, he'll need it."

"You're a good sister!" Mom calls after her.

Matt's room is just across the hall from hers. The door is half-open to allow air to circulate, so Katie just nudges it open. Matt is scribbling fiercely on a tablet. She comes up behind him and looks over his shoulder: no need for Mom's advice, he's clearly thought of diagrams himself. She puts the coffee on the desk in front of him, then throws herself down in the armchair to wait. She could check her phone to pass the time, but instead she considers his back. The movement of his shoulder blades beneath the thin material of his t-shirt is hypnotising.

At last, he throws down his stylus and leans back with a sigh. He spins his chair round and smiles at her.

"Hey, caterpillar. What have you been up to?"

"Not much, just tinkering with some stuff on WoW." He's trying not to look at her bare legs and bare shoulders, but Katie can feel his eyes on her. He's in shorts and a t-shirt, and she takes the opportunity to admire the shape of his calves.

"Yeah? What level are you now?"

"93, in Gorgrond. I'm gonna try for a record in getting from 93 to 97. The shortest I've found is eight minutes, but I'm pretty sure I can beat that." She crosses her legs to make them look longer and pushes out her chest - as much as she has of one, anyway. Mom says she only grew a proper rack after she had two kids. Katie's hoping not to have to resort to such drastic measures.

He's looking at her legs as he says, "Sure, go for it and send me the video." Then he turns aside to get his water bottle. He faces her as he uncaps it and tilts his head back to drink, exposing his throat. She watches his adam's apple bob. It's not a bad seduction technique on his part, though she'd like it even better if he did it while shirtless.

"Ugh, back to thermodynamics." Katie likes how dedicated he is. Plus, his specialty is chemistry and hers is physics, so they balance each other out nicely. "Thanks for the coffee - really thoughtful of you," he adds, giving it an appreciative glance.

Katie gets up and leans over to hug him - though not too much, since she's at the right height to press his face into her chest. That'll be a more effective move in a few years, hopefully, but Matt still goes pink.

"Anything for my favourite brother," she chirps. Matt has no idea how true that is.

~*~*~

The summer Katie turns fifteen, Matt very nearly gets a girlfriend.

Her name is Eleanor, and she has attractive chestnut brown hair and a laugh that makes people turn around in the street. She specialises in astrophysics, so she and Matt spend hours talking to each other about space travel and the theory of FTL. She wants to join the Garrison.

By winter break, she's stopped talking to him altogether. Two weeks into the spring term, she transfers. Matt doesn't know why, and Katie doesn't tell him. The details would only upset him.

~*~*~

Matt and Dad leave in two days. Three days after that, Katie goes back to school. It's time for Katie to give Matt his last present.

She crawls into bed with him at midnight, as usual. What's less usual is that she isn't wearing any clothes. Sneaking across the hallway totally naked was pretty exciting. She presses herself to his back - he wears a t-shirt to bed even in the sweltering summer heat, though she can feel him sweating - and wraps her bare leg over his.

She knows he's realised when he goes very, very still. She'd rather he rolled over and kissed her, but he's shy. Maybe he thinks he's being gentlemanly by letting her take the lead.

"I'm ready," she whispers in his ear. She runs her hand down his arm, feeling the downy hair, and entwines their fingers.

He lets her roll him over onto his back. His breath is shallow. His eyes catch the light from the window - it's a full moon. Katie pushes back the covers so she can climb on top of him.

"Katie," he says, quietly. He sounds lost. His hands are tense at his sides. Katie leans down and kisses him.

It's not their first kiss: that was when they were little and they used to kiss all the time. Then they never entirely stopped, though being at boarding school made it harder to have privacy. These days, Matt always lets her start it. He knows she likes being in control, but she's going to have to teach him the value of spontaneity in keeping romance alive.

He lets her part his lips with her tongue. She's got pretty good at this, if she does say so herself: Matt quickly starts to kiss back, tongue slipping gently across hers. Sometimes he likes to play dead fish to rile her up.

It doesn't take much to turn her on: a few minutes of kissing and she can feel she's wet between the legs. She wriggles about, parting Matt's thighs so she can settle on one and rock her hips back and forth. She's been doing this more often recently, getting Matt used to feeling her orgasm on top of him. It makes him hard every time, and he thrusts eagerly into her fist when she puts her hand down his shorts.

She gropes him through his pants and feels that he's hard. She deepens the kiss, riding his thigh harder, really grinding her clit against his solid leg. She's already so excited that she can feel the edge of pre-orgasmic ecstacy in her belly.

Matt's arms wrap around her - then come to rest on her ass, feeling her buttocks work as she grinds her hips back and forth. Climax hurtles towards her.

Her body jerks back and forth as she finally clears the jump, aching pleasure exploding in her abdomen and making her mouth open in silent ecstacy. She keeps moving, keeping wringing pulses and sparks from deep in her abdomen.

She relaxes at last, hips slowing to a tiny, lazy grind. But they're not done.

First, she strips Matt of his t-shirt, leaving him leaning up on his elbows. Then she strips him of his boxers.

"Katie, _what_ -" He can't say it too loud in case they wake up their parents, but the urgent raising and lowering of his eyebrows conveys his meaning.

"What do you think, dummy?" She shuffles so they're in the right position. "This is the most comfortable way for me," she explains, taking hold of his erection, "so I guess we'll see how it is for you. Do you think you can thrust in that position?"

"D-do - what about a condom?" Matt hisses, looking alarmed.

"I've been on the Pill for a year and a half!" She squeezes and strokes his erection to calm him down. She likes playing with his cock, especially the feeling of the smooth velvety skin over iron hardness. She swipes her thumb over the slit and spreads the wetness over the head.

Then she kneels up and positions the tip just at the entrance to her cunt. Then, slowly, she begins to sit down.

It goes in easier than her comparably-sized vibrator - something to do with the texture, maybe. But he still feels hard and huge inside her, impossible and unyielding. She opens her mouth and takes slow breaths, letting gravity do some of the work. Matt's eyes switch between being tightly closed and wide open, staring at where they're joined.

About halfway down, it starts to feel _really_ good - the head must be brushing her G-spot. She can feel her cunt clenching and relaxing around his cock.

Once it's all the way in, everything goes smoothly. It turns out Matt _can_ thrust from that position, and between the two of them they set up a rhythm instantly, rocking back and forth. It's so easy - why don't all the advice boards tell you it's _easy_? She can't kiss him, so she directs him to her breast, which he sets to sucking and biting with such fervour that she has to bite her lip not to cry out. It feels like they're one person, one mind. It feels _natural_.

She doesn't expect to come from it - women rarely do from intercourse - but something like a miniature orgasm, a tiny peak, washes over her as Matt thrusts over and over, stimulating her G-spot. Her entrance is sore, but she hardly notices it as sexual pleasure races through her body.

Matt comes suddenly, body seizing up and spasming, uttering guttural noises into her chest, fingers digging hard into her hips. A hard, punishing climax clenches all Katie's muscles, intense throbbing pleasure rocketing through her and bringing tears to her eyes.

When Matt collapses back onto the bed, his eyes are wet too. From the way he convulsed beneath her, she guesses it must have been intense for him too. She knows he was a virgin.

She lies down with him again and wraps herself up in his arms. They're both kind of sweaty, but she doesn't care. She likes the feeling of his semen trickling down her inner thigh: a condom would have been safer, but sometimes it's worth taking risks.

"You'll think of this when you're off adventuring through the solar system, won't you?" she asks, pressing her nose into his warm throat.

"Yeah." His adam's apple moves next to her cheek. "Yes, I'll think of it."


End file.
